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CPU Power Management for Intel Haswell Chips
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powerMgmt-haswellDesktop.md

These notes are for Intel Haswell desktop chips running Linux. YMMV depending on the specific processor and Linux distro/version.

PowerTOP

(User's Guide)

The following will generate a snapshot of everything powertop measures in a file called powertop.html, which can then be viewed in a web browser:

> sudo powertop --html

This includes commands for tuning the "tunables," which can be added to /etc/init.d/rc.local so that they are set during boot-up. Alternatively, the following will tune all tunables (there may be auto-tuned settings that fail to be set or are not optimal for a given system, some trial-and-error may be needed):

> powertop --auto-tune

Enabling power-save for network interfaces

  • To disable Ethernet Wake-on-LAN, add to /etc/udev/rules.d/71-disable_wol.rules:

      ACTION=="add", SUBSYSTEM=="net", KERNEL=="eth*", RUN+="/usr/local/sbin/ethtool -s %k wol d"

    %k is a specifier for the kernel name of the matched device. For example, if it finds that the rule is applicable to eth00, the %k specifier will be replaced with eth0. To apply the rules to only a particular interface, just replace the pattern eth* and specifier %k with the desired interface name.

    If not using eth0 and it's still draining power, turn off the interface (to have this happen at boot-up, add to /etc/init.d/rc.local):

      > sudo ifconfig eth0 down

    To turn eth0 on (reverse the above):

      > sudo ifconfig eth0 up

  • To enable power-save on wirless interfaces, add to /etc/udev/rules.d/71-wifi-powersave.rules:

      ACTION=="add", SUBSYSTEM=="net", KERNEL=="wlan*", RUN+="/usr/sbin/iw dev %k set power_save on

    %k is a specifier for the kernel name of the matched device. For example, if it finds that the rule is applicable to wlan0, the %k specifier will be replaced with wlan0. To apply the rules to only a particular interface, just replace the pattern wlan* and specifier %k with the desired interface name.

    If power-save for wireless interfaces still remains off, enable it manually:

      > iw wlan0 set power_save on

    If using the ath9k driver, this may report "command failed: Operation not supported (-95)." To fix this, add the following to /etc/modprobe.d/ath9k.conf:

      options ath9k ps_enable=1

References

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